Hi guys, I have a young 2 year old grafted paw paw tree and I want to know when should I prune it to encourage branching out? Right now it's only a single 3' tall twig that has just started showing signs of coming out of dormancy. If I do it should I top it in half above the graft line or I should just leave it alone to grow and will eventually branch out into the cone/triangular shape by it self? And when will it usually start bearing fruit from this grafted paw paw?

I'm aware that you need 2 for cross pollination of fruit bearing, but I have the cultivar "sunflower" that supposed to be self fertile. I know with another cultivar will be more productive, so I planned to graft another kind on to the one that I have now later to avoid having to plant another tree. Any help would greatly appreciated thank you in advance.

Seng